Quote Originally Posted by monkey spanners View Post
The flow switch will prevent the system running when there is no water flow in the condenser. This would be bad.
The lp and hp switches will turn the system off in the event of high or low pressure fault condidtions. This could be equally bad, people have been killed due to none working pressure switches.
The delay timer when suitably programed will prevent the compressor starting before the system pressures have had a chance to equalise, as your compressor will likely be a low starting torque version. (a hard start kit may be a worthwhile adition too)
The txv will better modulate refrigerant flow now that you will have a low head pressure (dictated by water temperature) and a variable evaporator load depending on air temp and frost accumilation. (a balanced port txv would be the best buy)
The frost stat together with the hot gas bypass valve will initiate and terminate a defrost cycle on the evaporator to keep it clear of excessive frost.
Reciever/reciever drier will provide a buffer for the excess refrigerant as the txv modulates.
Thermostat to turn it off and on as water temperature dictates.

So some of the 'complications' make the system safer for you and itself, and others make it more efficient.

You will also need an f gas certificate if you are in europe as its now illeagal to work on refrigerating systems without one, and as Brian pointed out R22 is now longer allowed in new systems, so a drop in replacement will be needed.


Jon
Excellent information, thanks. Re the high/low pressure switches, what pressures would you expect to see. I assume these switches are at preset pressures. From what I have read refrigerant pressure is related to differential in temperature so a 'working pressure' is impossible to determine unless the temperatures are known. So, I would assume that the switch would operate in case of excess pressure, but what pressure is classed as excess pressure and, as it is not a DC compressor how can the pressure be regulated?

Interestingly, studying the circuit of the unit that this 'split' came from the outdoor unit is very simple - it is simply switched on and off by the control board and has no feedback of information to the control board or any apparent safety features. It has an outdoor thermostat to control the fan and that's about it.

The internal unit has a pipe temperature and room temperature thermistor and that's it. There are no pressure sensors anywhere. Is this normal on older machines, this machine seems to be from around the mid 90's.

Re the system pressures equalising, surely in a non operating state there are no pressure differentials throughout the system and everything is in equilibrium, starting the compressor generates that differential and refrigerant starts to circulate or am I missing something?

Thanks for the information,

Nigel